Deep space network (DSN) receivers currently under development use phase locked loops (PLLs) to track the carrier, subcarrier, and symbol phase. Like most coherent receivers, the DSN receivers rely on lock detectors to provide the symbol lock status of its PLLs. Since carrier, subcarrier, and symbol synchronization need to be achieved before any meaningful symbol detection can be initiated, symbol lock detectors play a vital role in the final decision of accepting or rejecting the detected symbols. In the past, symbol lock detectors have employed overlapping symbol intervals in their operations and therefore require two integrators operating over staggered time intervals.
During operation, a loop is assumed to be locked when its lock indicator consistently has a positive status. The carrier and subcarrier lock detectors currently used in DSN receivers have already been analyzed. The present invention concerns the analysis of three new symbol lock detectors which simplify implementation for DSN receivers and two prior-art symbol lock detectors for comparison.